A vein authentication apparatus registers vein data and vein characteristic amounts, determines comparison order at vein data identification time by sorting records in descending order of degree of similarity on the basis of vein characteristic amounts for comparison and the registered vein characteristic amounts, and makes vein data comparison in accordance with the comparison order. The vein authentication apparatus uses 32 frequencies obtained by performing a Fourier transform, 12 angles obtained by performing a Fourier transform, curvature directions in 36 angle areas, segment directions in 18 angle areas, and a vein amount as the vein characteristic amounts. By doing so, the accuracy of comparison order is improved and a comparison using a record for which a degree of similarity is low can be omitted. As a result, the speed of a comparison process and the maximum number of pieces of living body information which can be registered can be increased.